Máirín Bean Uí Dhalaigh or Máirín O’Daly (née Máirín Nic Dhiarmada (30 November 1908 – 25 January 1994) was First Lady of Ireland from 1974 to 1976, as the wife of former Chief Justice of Ireland and 5th President of Ireland, Cearbhall Ó Dálaigh.
She was the eldest of four children of a Dublin father and Cork mother, born in Mussoorie, India, where her father was a teacher with the Royal Munster Fusiliers. At age two she was sent to her father's sister in Tralee. She was educated at various schools in Dublin, and studied Latin and Irish in University College Dublin (UCD). While there in 1931 she gave an address on "Women in Irish life long ago" which Philip O'Leary described in 2004 as "unapologetically feminist". She worked as a teacher before completing a masters in Old Irish. Thereafter she was on the faculty at UCD, and later also on the governing body. For the Irish Texts Society, she edited Cath Maige Mucrama and produced a glossary and corrections for The Life of Aodh Ruadh Ó Domhnaill. She also contributed to the Royal Irish Academy's Dictionary of the Irish Language.
She got to know Cearbhall Ó Dálaigh at UCD through the Literary and Historical Society, Conradh na Gaeilge and hillwalking club; in 1934 they were married. The couple had no children. In 1983, five years after her husband's death, she was appointed to the Council of State by his successor as President, Patrick Hillery. Her last years were blighted by ill health. She is buried with her husband in Sneem, County Kerry.